Jeremy Corbyn has accused Boris Johnson of arrogance, after the British Foreign Secretary said the European Union could "go whistle" if they make "extortionate" demands over Brexit.
Mr Johnson was responding in the House of Commons to questions over the proposed "divorce bill" which the UK is expected to receive next week as Brexit negotiations resume in Brussels.
European Commission president Jean-Claude Juncker has suggested that the bill, which covers outstanding liabilities for programmes which the UK signed up to as an EU member, as well as ongoing costs including staff pensions, could be around £50bn, while unconfirmed reports have claimed it could reach almost twice that figure.
Addressing Mr Johnson at foreign affairs questions in the Commons, Tory eurosceptic Philip Hollobone said the UK had made a net contribution of £209bn to the EU since joining in 1973, adding: "Will you make it clear to the EU that if they want a penny piece more then they can go whistle?"
Mr Johnson replied: "I'm sure that your words will have broken like a thunderclap over Brussels and they will pay attention to what you have said.
"He makes a very valid point and I think that the sums that I have seen that they propose to demand from this country seem to me to be extortionate and I think 'to go whistle' is an entirely appropriate expression."
Speaking outside the Commons chamber, Mr Corbyn said: "I think it is ridiculous for the Foreign Secretary to approach important and serious negotiations with that silly, arrogant language that he so often employs.
"Treat people with respect and there's a fair chance you will be treated with respect in return.
"If you start on the basis of those silly remarks, what kind of response does he expect to get?"
Mr Corbyn is due to meet the EU's chief Brexit negotiator Michel Barnier in Brussels on Thursday, to set out his party's approach to Brexit and hold "exploratory discussions" about the negotiations ahead.
He said Labour would "pay what we are legally required to pay", but nothing beyond that.
"We have to negotiate intelligently and sensibly, but above all negotiate with respect and expect to be respected in return," said Mr Corbyn.
The UK's negotiating team under Brexit Secretary David Davis is due to begin the first full round of negotiations with Mr Barnier on Monday.